Amphibious vehicles are dual role vehicles having wheels or tracks for moving on land and a water tight hull with a water propulsion means for moving across the water. The inherent challenge of amphibious vehicles is providing sufficient buoyancy to counteract the weight of the vehicle in a vehicle shape suitable for navigating on land. With ordinary amphibious vehicles, a water tight hull provides sufficient water displacement to permit the amphibious vehicle to navigate through the water even if the hull closely resembles the land base equivalent. Additional floatation devices are often attached to the amphibious vehicles during aquatic travel to improve the ratio of the vehicle weight to the water displacement and removed from the vehicle for travel across land.
With armored military vehicles, the additional weight of the armor plating can increase the weight of the vehicle past the maximum possible buoyancy generated by water displacement alone. Similarly, amphibious military vehicles are often employed in situations where the vehicle must quickly alternate between aquatic and land travel or under fire when leaving or entering the water making the attachment or removal of floatation devices impractical or dangerous.
In order to mitigate the effects of the heavier armor required under current threat conditions, many conventional and amphibious armored vehicles often have heavier armor plating at the sides of the vehicle with thinner armor on the top and bottom of the vehicle. The arrangement maximizes protection on the sides of the vehicle most likely to be struck by ballistic threats while reducing the overall armor and weight of the vehicle by providing thinner armor on the portion of the vehicle least likely to be struck. However, the increased use of improvised explosive devices (“IEDs”) and other mine-type weapons that exploit the thinner belly armor have dramatically increased in recent years presenting a substantial risk. The contrasting concern is that adding additional armor to the belly armor can reduce the buoyancy of the vehicle.
Trim vanes are often employed to account for the poor buoyancy of the armored amphibious vehicles. As depicted in FIGS. 1 and 2, trim vanes 104 are most commonly positioned on the bow 102 of amphibious vehicle 100 such that the vane 104 can be positioned to extend forward and upwards from the bow 102 when the amphibious vehicle 100 is to be operated in water. The bow trim vanes 104 prevent water from coming over the bow 102 of the vehicle 100 and swamping the vehicle 100. Certain trim vanes 104 can also increase the effective length of the vehicle 100 improving the water displacement of the vehicle 100 and accordingly the buoyancy of the vehicle 100. The inherent drawback of the bow 102 mounted trim vanes 104 is that the upward orientation of the trim vanes 104 can interfere with the driver's vision. The trim vanes 104 are lowered and secured to avoid bouncing into the driver's vision during travel on land often requiring vehicle personnel to move to the bow 102 of the vehicle 100 and manually lower the trim vane 104 thus exposing the personnel to hostile fire.
The trim vanes are also often mounted at the stern of both watercraft and amphibious vehicles to adjust the direction the propulsion system outflow (herein referred to as vectoring) and change the longitudinal pitch of the vehicle (herein referred to as trim) to cause the vehicle to ride higher in the water to reduce drag and improve the buoyancy of the vehicle. However, the robust construction of both bow and stern mounted trim vanes necessary to withstand the hydrodynamic forces pushing against the vehicle during aquatic travel can substantially increase the weight of the vehicle thereby often offsetting the improved buoyancy. Similarly, many stern mounted trim vanes are fitted with an extension/retraction assembly that folds the trim vane against the rear of the vehicle during travel across land when the trim vane is not in use to prevent damage to the trim vane from obstacles during travel. The added weight of the extension/retraction assembly further increases the overall weight of the vehicle and worsens the overall buoyancy of the vehicle. Moreover, with many armored amphibious vehicles, the ingress/egress point for the vehicle is at the rear of the vehicle, which can be blocked or impeded by the refracted trim vane. As such, the trim vane must often be lowered to permit occupants to enter or exit the vehicle significantly slowing the process particularly if obstacles impede the lowering of the trim vane.
Although trim vanes are currently employed to improve the buoyancy of armored amphibious vehicles, the presently available trim vanes have significant drawbacks and can interfere with the vehicles function. Moreover, use of trim vanes frequently require a reduction in armor due to the overall weight of the vehicle thus increasing the risk for armored amphibious vehicles from IEDs and other explosives.